Components of a General-Purpose Computer with Block Diagram

A general-purpose computer is a computer designed to perform a variety of tasks based on stored programs, consisting of input, output, memory, processing, and control units.

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Components of a General-Purpose Computer

A general-purpose computer consists of the following major components:

• Input Unit – Accepts data and instructions from the user (e.g., keyboard, mouse)
• Output Unit – Displays or delivers processed results to the user (e.g., monitor, printer)
• Memory Unit – Stores data and instructions temporarily (RAM) or permanently (ROM/Hard Disk)
• Central Processing Unit (CPU) – The brain of the computer, which contains:
  • Arithmetic Logic Unit (ALU) – Performs arithmetic and logical operations
  • Control Unit (CU) – Directs and coordinates all computer operations
  • Registers – Small, fast storage locations inside the CPU (PC, IR, AC, etc.)
• Bus System – Communication pathways connecting all components (data bus, address bus, control bus)

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Block Diagram of a General-Purpose Computer

All components are connected via a system bus (Data Bus, Address Bus, Control Bus).

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Functions of PC, IR, and AC Registers

a) PC – Program Counter

• PC is a register that holds the address of the next instruction to be fetched from memory.
• After each instruction is fetched, the PC is automatically incremented to point to the next instruction.
• It ensures instructions are executed in the correct sequence.

b) IR – Instruction Register

• IR is a register that holds the current instruction being executed.
• Once an instruction is fetched from memory, it is placed in the IR for decoding by the control unit.
• The control unit reads the IR to determine what operation to perform and on which operand.

c) AC – Accumulator

• AC is a general-purpose register that holds the intermediate results of arithmetic and logical operations performed by the ALU.
• It acts as a temporary storage during computation.
• Most ALU operations use the AC as both a source and destination for data.

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Conclusion

A general-purpose computer works through the coordinated functioning of input, output, memory, and CPU components. Registers like PC, IR, and AC play a crucial role in the fetch-decode-execute cycle, ensuring smooth and sequential instruction processing.